Single screw in situ fixation for the management of slipped upper femoral epiphysis was introduced in 1990 and has been reported to result in a decreased incidence of avascular necrosis and chondrolysis compared to previous methods using multiple pin fixation with or without osteotomy. To investigate this we retrospectively reviewed two groups of patients. Group A (44 patients, 55 hips) was treated over a 27-year period (1963-1989). Forty-four hips were treated with multiple pins and 11 hips had primary intra- or extracapsular osteotomy with multiple pin fixation. Group B (83 patients, 106 hips) was treated over a 7-year period (1999-2005) with single screw fixation without osteotomy. All patients were followed up for at least 2 years. In group A avascular necrosis occurred in eight hips (14.5%); five occurred after osteotomy; two after forceful manipulation; and one was due to pinning in the posterosuperior quadrant of the femoral head. Chondrolysis occurred in 14 hips (25%), of which six (11%) were due to persistent pin penetration, and in eight (14%) chondrolysis was present at presentation (before treatment). In group B avascular necrosis occurred in only two hips (2%); both were severe, unstable slips. Chondrolysis occurred in ten hips (10%) of which two (2%) were due to persistent pin penetration, and eight (8%) had chondrolysis at presentation We conclude that single screw fixation is a safer technique than multiple pin fixation or osteotomy. Without osteotomy avascular necrosis only occurs in severe, unstable slips. Chondrolysis due to pin penetration is almost eradicated. Chondrolysis at presentation, however, is still prevalent and occurs in female patients with severe, chronic slips.

This study has University of Cape Town Research Ethics Committee approval REC REF 086/2007. This article is the sole work of the authors. No benefits of any form are to be received from a commercial party related directly or indirectly to the subject of this article.